Suspension system for a vehicle including an accumulator
Suspension system for a vehicle is disclosed and claimed. The suspension system includes a fluid, a suspension strut, a hydraulic cavity, an accumulator, and a volume modulator. The hydraulic cavity is at least partially defined by the suspension strut and is adapted to contain a portion of the fluid. The hydraulic cavity supplies a suspending spring force that biases a wheel of a vehicle toward the road surface. The volume modulator selectively pushes the compressible fluid into the hydraulic cavity and vents the compressible fluid from the hydraulic cavity, thereby actively modulating the suspending spring force.
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The present invention is a continuation-in-part of International Application No. PCT/US01/48488, filed 07 Dec. 2001 and entitled “Suspension System For A Vehicle”, which claims benefit of U.S. provisional application Ser. No. 60/251,951, filed 07 Dec. 2000 and entitled “Compressible Fluid Strut”.
TECHNICAL FIELDThe subject matter of this invention generally relates to suspension systems for a vehicle and, more particularly, to suspension systems including an accumulator adapted to contain a portion of a fluid at a predetermined pressure above atmospheric pressure.
BACKGROUNDIn the typical vehicle, a combination of a coil spring and a gas strut function to allow compression movement of a wheel toward the vehicle and rebound movement of the wheel toward the ground. The suspension struts attempt to provide isolation of the vehicle from the roughness of the road and resistance to the roll of the vehicle during a turn. More specifically, the typical coil spring provides a suspending spring force that biases the wheel toward the ground and the typical gas strut provides a damping force that dampens both the suspending spring force and any impact force imparted by the road. Inherent in every conventional suspension strut is a compromise between ride (the ability to isolate the vehicle from the road surface) and handling (the ability to resist roll of the vehicle). Vehicles are typically engineered for maximum road isolation (found in the luxury market) or for maximum roll resistance (found in the sport car market). There is a need, however, for an improved suspension system that avoids this inherent compromise.
The following description of the preferred embodiment of the invention is not intended to limit the invention to the preferred embodiment, but rather to enable any person skilled in the art of suspension systems to use this invention.
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The compressible fluid 12 of the preferred embodiment, which cooperates to supply the suspending spring force, is preferably a silicon fluid that compresses about 1.5% volume at 2,000 psi, about 3% volume at 5,000 psi, and about 6% volume at 10,000 psi. Above 2,000 psi, the compressible fluid has a larger compressibility than conventional hydraulic oil. The compressible fluid, however, may alternatively be any suitable fluid, with or without a silicon component, that provides a larger compressibility above 2,000 psi than conventional hydraulic oil.
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The cavity piston 32 of the preferred embodiment is preferably coupled to the displacement rod 30 and preferably extends to the hydraulic tube 28. In this manner, the cavity piston 32 separates the inner cavity 38 into a first section 40 and a second section 42. The cavity piston 32 defines a first orifice 44 and a second orifice 46, which both preferably extend between the first section 40 and the second section 42 of the inner cavity 38. The first orifice 44 and the second orifice 46 function to allow flow of the compressible fluid 12 between the first section 40 and the second section 42 of the inner cavity 38. The cavity piston 32 is preferably securely mounted to the displacement rod 30 by a conventional fastener 48, but may alternatively be integrally formed with the displacement rod 30 or securely mounted with any suitable device. The cavity piston 32 is preferably made from conventional materials and with conventional methods, but may alternatively be made from other suitable materials and with other suitable methods.
The first variable restrictor 34 of the preferred embodiment is coupled to the cavity piston 32 near the first orifice 44. The first variable restrictor 34 functions to restrict the passage of the compressible fluid 12 through the first orifice 44 and, more specifically, functions to variably restrict the passage based on the velocity of the cavity piston 32 relative to the hydraulic tube 28. In the first preferred embodiment, the first variable restrictor 34 is a first shim stack 50 preferably made from conventional materials and with conventional methods. In alternative embodiments, the first variable restrictor 34 may include any other suitable device able to variably restrict the passage of the compressible fluid 12 through the first orifice 44 based on the velocity of the cavity piston 32 relative to the hydraulic tube 28. The second variable restrictor 36 of the preferred embodiment is coupled to the cavity piston 32 near the second orifice 46. The second variable restrictor 36—like the first variable restrictor 34—functions to restrict the passage of the compressible fluid 12 through the second orifice 46 and, more specifically, functions to variably restrict the passage based on the velocity of the cavity piston 32 relative to the hydraulic tube 28. In the preferred embodiment, the second variable restrictor 36 is a second shim stack 52 preferably made from conventional materials and with conventional methods. In alternative embodiments, the second variable restrictor 36 may include any suitable device able to variably restrict a passage of the compressible fluid 12 through the second orifice 46 based on the velocity of the cavity piston 32 relative to the hydraulic tube 28.
The cavity piston 32, the first orifice 44, and the first variable restrictor 34 of the preferred embodiment cooperate to supply the rebound damping force during the rebound movement of the wheel 22. The rebound damping force acts to dampen the suspending spring force that tends to push the displacement rod 30 out of the hydraulic tube 28. The cavity piston 32, the second orifice 46, and a second variable restrictor 36, on the other hand, cooperate to supply the compression damping force during the compression movement of the wheel 22. The compression damping force acts to dampen any impact force that tends to push the displacement rod 30 into the hydraulic tube 28.
The suspension strut 14 of the preferred embodiment is further described in U.S. application filed on 07 Dec. 2001, entitled “Compressible Fluid Strut”, and assigned to Visteon Global Technologies, Inc. As described in that application, the suspension strut may include a pressure vessel and may include a valve. In alternative embodiments, the suspension strut may include any suitable device to allow active modulation of the suspending spring force with compressible fluid.
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The volume modulator 20 of the preferred embodiment also includes a cavity-side valve 68 coupled between the hydraulic line and the volume modulator 20 and an accumulator-side valve 70 coupled between the reservoir and the volume modulator 20. The cavity-side valve 68 and the accumulator-side valve 70 function to selectively restrict the passage of the compressible fluid. Preferably, the cavity-side valve 68 and the accumulator-side valve 70 are so-called poppet valves that may be actuated at relatively high frequencies. Alternatively, the cavity-side valve 68 and the accumulator-side valve 70 may be any suitable device that selectively restricts the passage of the compressible fluid at an adequate frequency.
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During the operation of the vehicle, it may be advantageous to neither increase nor decrease the suspending spring force. Since the motor 66, the eccentric 64, and the modulator pistons 62 are continuously moving, the accumulator-side valve 70 and the volume modulator 20 can also cooperate to draw compressible fluid 12 from the reservoir (shown in
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The suspension system 10 of the preferred embodiment also includes a reservoir 86 connected to the crank cavity 80. The reservoir 86 functions to contain a portion of the compressible fluid 12 at atmospheric pressure. With this arrangement, the accumulator 18 is preferably re-charged with leaked fluid from the crank cavity 80 and atmospheric fluid from the reservoir 86.
As any person skilled in the art of suspension systems will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiment of the invention without departing from the scope of this invention defined in the following claims.
Claims
1. A suspension system for a vehicle having a wheel contacting a surface under the vehicle and a suspension link suspending the wheel from the vehicle and allowing relative movement of the wheel and the vehicle, said suspension system comprising:
- a suspension strut adapted to couple the suspension link and the vehicle;
- a hydraulic cavity at least partially defined by said suspension strut and adapted to contain a portion of a fluid and to supply a suspending spring force that biases the wheel toward the surface;
- an accumulator adapted to contain a portion of the fluid at a predetermined pressure above atmospheric pressure;
- a volume modulator in fluidic communication with said hydraulic cavity and said accumulator and adapted to selectively push the fluid into said hydraulic cavity and vent the fluid from said hydraulic cavity, thereby actively modulating said suspending spring force, wherein said volume modulator includes a modulator housing defining a modulator cavity, a crankshaft, a modulator piston coupled to said crankshaft and adapted to cycle through a compression stroke and ar expansion stroke within said modulator cavity, a cavity-side valve coupled between said hydraulic cavity and said volume modulator and adapted to selectively restrict the passage of the fluid between said hydraulic cavity and said modulator cavity, and an accumulator-side valve coupled between said accumulator end said volume modulator and adapted to selectively restrict the passage of the fluid between said reservoir and said modulator cavity;
- a compressible fluid; wherein said hydraulic cavity is further adapted to cooperate with said compressible fluid to supply the suspending spring force.
2. The suspension system of claim 1 wherein said compressible fluid includes a silicone fluid.
3. The suspension system of claim 1 wherein said compressible fluid has a larger compressibility above 2,000 psi thin hydraulic oil.
4. The suspension system of claim 1 wherein said compressible fluid is adapted to compress about 1.5% volume at 2,000 psi, about 3% volume at 5,000 psi, and about 6% volume at 10,000 psi.
5. The suspension system of claim 1 wherein said suspension strut includes a displacement rod adapted to move into said hydraulic cavity and to compress said compressible fluid upon the relative movement of the wheel and the vehicle.
6. The suspension system of claim 5 wherein said displacement rod includes a cavity piston adapted to supply a damping force.
7. The suspension system of claim 1 wherein sold hydraulic cavity is defined by said suspension strut and a first hydraulic line adapted to communicate the fluid between said suspension strut and said volume modulator.
8. The suspension system of claim 1 wherein said volume modulator further includes an atmospheric seal adapted to seal said crankshaft and said modulator housing.
9. The suspension system of claim 8 wherein said volume modulator further includes a fluid bearing located between said modulator piston and said atmospheric seal and adapted to mount said crankshaft to said modulator housing for rotational movement.
10. The suspension system of claim 9 wherein said modulator housing, said atmospheric seal, and said fluid bearing define a crank cavity.
11. The suspension system of claim 10 further comprising a reservoir in direct fluidic communication with said crank cavity and adapted to contain a portion of the fluid at atmospheric pressure.
12. The suspension system of claim 10 further comprising a second hydraulic line adapted to communicate the fluid between said crank cavity and said accumulator.
13. The suspension system of claim 10 further comprising a pump coupled between said crank cavity and said accumulator and adapted to pump fluid into said accumulator.
14. The suspension system of claim 13 further comprising an electric motor driving said crankshaft and said pump.
15. The suspension system of claim 1 wherein said volume modulator further defines a crank cavity, and wherein at least a portion of said crankshaft is located in said crank cavity.
16. The suspension system of claim 15 further comprising a second hydraulic line adapted to communicate the fluid between said crank cavity and said accumulator.
17. The suspension system of claim 15 further comprising a pump connected coupled between said crank cavity and said accumulator and adapted to pump fluid into said accumulator.
18. The suspension system of claim 17 further comprising an electric motor coupled to said crankshaft and to said pump.
19. A volume modulator of claim 1, wherein the volume modulator is positioned between the hydraulic cavity and the accumulator to regulate the fluid flow therebetween.
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- See Attachment “A”.
- See Attachment “B”.
Type: Grant
Filed: Aug 20, 2002
Date of Patent: May 3, 2005
Patent Publication Number: 20020195789
Assignee: Visteon Global Technologies, Inc. (Dearborn, MI)
Inventors: Joshua D. Coombs (Whitmore Lake, MI), Jeremy Edmondson (Canton, MI)
Primary Examiner: Paul N. Dickson
Assistant Examiner: Toan C To
Attorney: Brinks Hofer Gilson & Lione
Application Number: 10/224,245